Electric switch.



F. KRAZ & G. HONOLD.

mimmo swncH. APPL|cAr1oN`r|LED APR'. 2. 1916.

Patented Aug. '27, ISHS'.

2 SHEETS-SHEET l.

nvewrow F. KRATZ & G. HONOLD.

ELECTRIC SWITCH.

APPLICATION msn APR. l2. 191e.

Patented Aug. 2T, 19H3'.

2 SHEETS-SHEET 2.

Forza:

UNITED STATES FRANZ XRATZ AND GOTTLOIB HON OLD,` STUTTGART, GERMANY, ASSIGNORS TO THE FIRM OF ROBERT BOSCH, OF STUTTGART, GERMANY.

ELECTRIC SWITCH.

Patented Aug. 27., 1918.

Original 'application led March 9, y1915, Serial No. 13,2400. Divided and this application led April 12, n 211916.` SerialNo.90,740. Y

To ZZ whom z't may concern:

Be 1t known 'that we, FRANZ KnArzand GorrLoB HoNoLD, both subjects of the Eml peror of Germany, `residing at Stuttgart, Germany, have invented certain newand useful Improvements in ElectricV Switches,

of which the following is a full, clear, and

exact description, such as will enable others skilled in the art to which it appertains to make and use the same. l.

This application is a division of our application Serial No. 13,200 filed March 9, 1915, and it is directed to the arrangement of resistance material in a motor .starti-ng'fswitch for internal'combustion engines on aut0mo-' y :l arrangement of the resistance strip therein.

biles, motor boats and other moving vehicles.

` This resistance material must have large carrying capacity, inasmuch as the motor current required to overcome the static friction and the resistance imposed by the compressed gas in, the cylinders sometimes reaches 200 to 500 ampere's, depending upon the size of the engine. The large amount oi heat suddenly generated in the resistance material as a result of this large momentary .Y

current must be dissipated,and it has therefore been customary heretofore to arrange the resistance as a separate unit apart from the switch, so that it is freely exposed to the cooling effects of the atmosphere. This prior arrangement is of considerable disadvantage in automobiles and motor boats where room is quite limited and complexity is to be avoided, because the resistance coils or grids require considerable free space and the electrical connections from the switch are troublesome.

In accordance with the present invention, the resistance is combined with the switch and yet proper provision is made for the rapid dissipation of the heat and for the reliable support of the resistance at all times. lVe accomplish these results by laying flat strips of resistance material around the sides and bottom of the switch casing away from interference with the operating parts of the switch, the resistance material being held in place between insulating material by a met-al cover secured to an inner casing by fastening means passing between the strips. The ends of the strip are brought to bin ing posts'on the back of the switchcasing through openings. which furnish passages for air currents, so that the strip is suitably ventilated and the terminals thereof located away from the operator.

In the accompanying drawings illustrating a Apreferred form of our invention, Figure l is a sectional elevation through the switch in depressed position; Fig. 2 isa section on line 2-2 of Fig. 1;. Fig. 3' isang enlarged section on line 3 3 of Fig. 1; Fig.. 4 is a rear elevation of the switch, partly broken away; Fig. 5 is an elevatiorrofpue".l

side of the switch with the outer'casingremoved; Fig. 6 is an elevation of' the other. side of the switch, with some of theparts4 partly broken away; and Fig. 7 is a sectionv through the casing particularlyv showing the terminate in horizontal locking slots t into which the tongues g' may be turned to lock the switch shaft against depression from its raised position, the lock-bar e being longitudinally movable with the switch shaft and rotatable therein. The spring tends to hold the switch shaft b in its raised position. The switch shaft Z) carries the conducting switch bridge Z and also an arm Z which cooperates with the conducting switch bridge Z2. The contact studs m are mounted on the insulating material fw and are electrically connected to the binding-posts m. The switch bridge Z2 is adapted to maintain a set position, throughout a portion of the stroke of the switch shaft o, and to,.move therewith when the arm Z engages the upper or lower rim of the sleeve Z3 which is fast with the switch bridge -Z2 and slidable on the post i. The switch bridges Z and Z2 are each composed of bent laminations of thin metal riveted together at Z4L and held between two clamping plates with fianges p. The insulation Z insulates the switch shaft b and the posts z' and c from the switch bridges Z and Z2. The nut o screwed on the end of the switch shaft forces the switch bridge against the member o.

A continuous Strip 1- of nickelin or other suitable resistance metal, is laid around the sides and bottom of the switch-housing a. The folded strip is insulated on both surfaces by mica plates s and the outside is covered by a metal sheet u fastened to the switch-housing a by rivets u extending between the strips. The two ends of the strip fr -are brought through openings a: in the back a of the switch casing, andare connected to the binding-posts 'v andm.-

Inasmuch as the resistance material 1' is called upon to carry the entire motor starting current, which, in some cases, may reach 200 to 500 amperes, the heat generated is considerable, and must be dissipated in order to prevent warping of the strip' and possible short-circuit thereof, and also so as not to overheat the operating parts of the switch. We have found that the openings :v in theback of the switch casing rovide sufiiciently well for the passa e o air around the strip r in the casing an thereby prevent a hazardous temperature rise in the strip. Furthermore the rivets 'w' hold the folds of the strip rigidly in place, and thereby rel sist the tendency of the strip to warp when heated.

Having thus described our invention, what we claim is:

1. In an electric motor starting system for engines, the combination with a starting switch, of ahousing therefor providing a channel insulated on opposite walls, a strip Copies of this patent may be obtained for ive cents eiih, by addressing the "Commissioner o! Intenta,V

resistance in said channel, and fastening means drawing the opposite insulated walls into firm contact with the strip resistance to hold it in place upon temperature changes therein.

2. In an electric motor starting system for engines, .the combination with a switch, of a housing therefor providing a channel with an opening-to the atmosphere, and a strip resistance arranged in the channel and passingl loosely through said openV posite-insu ated walls into firm contact with the strip resistance, whereby the strip resistanceis heldrmly in place in the chan-V nel upon temperature changes therein, and the heat generated is dissipated by air passin into t e channel from ,the atmosphere.

witness whereof, We aix oursignatures.

FRANZ KRATZ. GOTTLOB HONOLD.

Washington, D. 0. 

